Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
  • H01L33/50—Wavelength conversion elements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
  • H01L2933/0008—Processes
  • H01L2933/0033—Processes relating to semiconductor body packages
  • H01L2933/0041—Processes relating to semiconductor body packages relating to wavelength conversion elements

Definitions

• the present disclosure is directed generally to light emitting diodes and methods for manufacturing light emitting diodes.
• LEDs Light emitting diodes
• White light LEDs can also be used in general lighting, architectural, outdoor, commercial, and/or residential illumination.
• True white light LEDs are not available because LEDs typically only emit at one particular wavelength. For human eyes to perceive the color white, a mixture of wavelengths is needed.
• One conventional technique for emulating white light with LEDs includes depositing a light conversion material (e.g., a phosphor) on a base material (e.g., indium gallium nitride (InGaN)).
• a light conversion material e.g., a phosphor
• a base material e.g., indium gallium nitride (InGaN)
• the InGaN base material emits a blue light that stimulates the light conversion material to emit a yellow light. Because yellow light stimulates the red and green receptors of a human eye, the resulting mix of blue and yellow light gives the appearance of white to the eye if the base material and light conversion material are matched appropriately. If not matched appropriately, however, the combined emissions appear off white and may reduce color fidelity of electronic devices.
• Figure 1A is a partially schematic illustration of a representative microelectronic workpiece carrying microelectronic devices configured in accordance with embodiments of the technology.
• Figure IB is a schematic illustration of a microelectronic device singulated from the workpiece shown in Figure 1 A.
• Figures 2A-6 illustrate various stages of a method for selectively applying light conversion materials onto LEDs in accordance with embodiments of the technology.
• Figure 7 is a partially schematic, top view of a portion of a microelectronic workpiece after selectively applying light conversion materials onto an LED in accordance with another embodiment of the technology.
• Figure 8 is a partially schematic, top view of a portion of a microelectronic workpiece after selectively applying light conversion materials onto an LED in accordance with still another embodiment of the technology.
• microelectronic workpiece is used throughout to include substrates upon which and/or in which microelectronic devices, micromechanical devices, data storage elements, read/write components, and other features are fabricated.
• Substrates can be, for example, semiconductive pieces (e.g., silicon wafers, gallium arsenide wafers, or other semiconductor wafers), nonconductive pieces (e.g., various ceramic substrates), or conductive pieces.
• Semiconductive pieces e.g., silicon wafers, gallium arsenide wafers, or other semiconductor wafers
• nonconductive pieces e.g., various ceramic substrates
• conductive pieces e.g., various ceramic substrates
• Figure 1A is a microelectronic workpiece 100 in the form of a semiconductor wafer 110 that includes multiple microelectronic devices or components 120. At least some of the processes described below may be conducted on the microelectronic workpiece 100 at the wafer level, and other processes may be conducted on the individual microelectronic devices 120 of the microelectronic workpiece 100 after the devices 120 have been singulated from the larger wafer 110. Accordingly, unless otherwise noted, structures and methods described below in the context of a microelectronic workpiece can apply to the wafer 110, the devices 120 that are formed from the wafer 110, and/or an assembly of one or more devices 120 attached to a support member.
• Figure IB is a schematic illustration of an individual device 120 after it has been singulated from the wafer 110 shown in Figure 1A.
• the device 120 can include operable microelectronic structures, optionally encased within a protective encapsulant.
• the device 120 can include an InGaN and/or other types of LEDs, transistors, capacitors, color filters, mirrors, and/or other types of electrical/mechanical/optical components.
• the device 120 can be electrically connected to external structural devices by pins, bond pads, solder balls, redistribution structures, and/or other conductive structures.
• FIGS 2 A-6 illustrate various stages of a method for selectively applying light conversion materials onto LEDs in accordance with embodiments of the technology.
• one or more light conversion materials or converter materials e.g., phosphor
• phosphor generally refers to a material that can sustain glowing after exposure to energized particles (e.g., electrons and/or photons).
• the light conversion material(s) can be patterned or selectively applied onto each LED to help compensate for color variances across the wafer. Further, the color(s) of the individual components on the wafer can be precisely tuned or controlled using the methods described herein.
• Figure 2A is a partially schematic, top plan view of a portion of a microelectronic workpiece 200 at an initial processing stage before any light conversion material has been applied onto the workpiece 200.
• Figure 2B is a partially schematic, side cross-sectional view taken substantially along line 2B-2B of Figure 2A.
• the microelectronic workpiece 200 includes a semiconductor substrate 202 having a front or active side 204 ( Figure 2B) and an LED 210 (e.g., an InGaN LED) formed at the front side 204 ( Figure 2B).
• an LED 210 e.g., an InGaN LED
• the workpiece 200 can include several features generally similar to the workpiece 100 described above with reference to Figures 1A and IB.
• the substrate 202 can be a semiconductor wafer with a plurality of microelectronic devices or components (e.g., LEDs 210) arranged in a die pattern on the wafer.
• Individual LEDs 210 also include terminals 212 (e.g., bond pads as shown in Figure 2A) and circuitry (not shown) electrically coupled to the terminals 212.
• One technique for forming the InGaN LEDs can include sequentially applying N-doped GaN, InGaN, and P-doped GaN materials on a sapphire (A1 2 0 3 ) and/or silicon (Si) substrate via epitaxial growth in a metal organic chemical vapor deposition (MOCVD) process. In other embodiments, however, other suitable techniques may be used to form the LED 210.
• Light conversion materials can be selectively applied to the LED 210 using a variety of different methods. In the illustrated embodiment, for example, a first mask or reticle 220 is positioned over the LED 210.
• the first mask 220 includes a plurality of apertures or openings 222 corresponding to a desired pattern for a first light conversion material (not shown— described in detail below with reference to Figures 3 A and 3B) on the LED 210.
• the first mask 220 can be a discrete component spaced apart from an upper surface of the LED 210, or the mask 220 may be composed of a photoresist material or other suitable mask material applied on the upper surface of the LED 210 (as shown in broken lines in Figure 2B) and patterned using photolithography and/or other suitable techniques.
• the terminals 212 can also be masked off to prevent shorting or contamination during processing.
• a first light conversion material or first converter material 224 (e.g., yellow phosphor) is applied in a desired pattern on the LED 210.
• the first light conversion material 224 can be applied using a screen printing process and/or other suitable methods.
• the first mask 220 is configured to exclude certain contact areas such that the first light conversion material 224 is selectively applied onto only desired regions of the LED 210.
• the first light conversion material 224 comprises a plurality of blocks or "islands" arranged in a selected pattern on the LED 210.
• the individual portions of the first light conversion material 224 are separated from each other by a plurality of first gaps or channels 225.
• the pattern shown in Figures 3 A and 3B is merely representative of one particular pattern for the first light conversion material 224.
• the first light conversion material 224 can be applied onto the LED 210 in a wide variety of different patterns or arrangements.
• the first light conversion material 224 can have a composition that emits at a desired wavelength when stimulated.
• the first light conversion material 224 can include a phosphor containing Cerium(III)-doped Yttrium Aluminum Garnet (Ce:YAG or YAG:Ce) at a particular concentration.
• Cerium(III)-doped Yttrium Aluminum Garnet Ce:YAG or YAG:Ce
• Such a material can emit a broad range of colors from green to yellow and to red under photoluminescence.
• the first light conversion material 224 can include Neodymium-doped YAG, Neodymium-Chromium double-doped YAG, Erbium-doped YAG, Ytterbium-doped YAG, Neodymium-cerium double-doped YAG, Holmium-chromium-thulium triple-doped YAG, Thulium-doped YAG, Chromium(IV)-doped YAG, Dysprosium-doped YAG, Samarium-doped YAG, Terbium-doped YAG, and/or other suitable phosphor compositions.
• the first light conversion material 224 can include Europium phosphors (e.g., CaS:Eu, CaAlSiN 3 :Eu, Sr 2 Si 5 N 8 :Eu, SrS:Eu, Ba 2 Si 5 N 8 :Eu, Sr 2 Si0 4 :Eu, SrSi 2 N 2 0 2 :Eu, SrGa 2 S 4 :Eu, SrAl 2 0 4 :Eu, Ba 2 Si0 4 :Eu, Sr 4 All 4 0 25 :Eu, SrSiAl 2 0 3 N:Eu, BaMgAli 0 Oi 7 :Eu, Sr 2 P 2 0 7 :Eu, BaS0 4 :Eu, and/or SrB 4 0 7 :Eu).
• the foregoing list of light conversion materials is not exhaustive.
• the phosphor material may also be mixed in a suitable carrier material (epoxy, silicone, etc.
• the first light conversion material (and any subsequent light conversion materials) can be selectively applied to the LED 210 using a number of different methods.
• a phosphor material e.g., Ce:YAG
• a photosensitive material e.g., PVA and ammonium dichromate
• a photolithographic procedure can be used to selectively expose portions of the composition such that the exposed portions are "fixed" at desired locations on the LED 210 to form the first light conversion material 224.
• This apply/expose/develop process can be repeated any number of times to selectively apply additional light conversion materials onto the LED 210.
• Still another suitable technique for selectively applying the first light conversion material 224 comprises spinning a photoresist material onto the LED 210 and patterning the material to form openings over desired areas or regions of the LED 210.
• the first light conversion material 224 can be applied into the openings and onto the LED 210 using electrophoresis or another suitable process. After applying the first light conversion material 224, the photoresist can be removed.
• some other suitable material may be applied onto the LED 210 and the openings can be selectively formed using excimer laser ablation or another suitable process.
• other suitable techniques may be used to selectively apply the first light conversion material 224 (and any subsequent light conversion materials) onto the LED 210.
• a second mask or reticle 230 is positioned over the LED 210.
• the second mask 230 includes a plurality of apertures or openings 232 corresponding to a desired pattern for a second light conversion material (not shown— described in detail below with reference to Figures 5 A and 5B) on the LED 210.
• the second mask 230 can be a discrete component spaced apart from an upper surface of the LED 210, or the second mask 230 may be composed of a photoresist material or other suitable mask material applied on the upper surface of the LED 210 and patterned using photolithography and/or other suitable techniques.
• a second light conversion material 234 (e.g., red phosphor) is selectively applied in a desired pattern on the LED 210.
• the second light conversion material 234 comprises a plurality of blocks or "islands" arranged in a selected pattern on the LED 210 in which the second light conversion material 234 may or may not contact adjacent portions of the first light conversion material 224.
• the individual portions of the second light conversion material 234, for example, can be separated from each other and the first light conversion material 224 by a plurality of second gaps or channels 235.
• the pattern shown in Figures 5 A and 5B is merely representative of one particular pattern for the second light conversion material 234.
• the second light conversion material 234 can be applied onto the LED 210 in a wide variety of different patterns or arrangements.
• the second light conversion material 234 can be composed of materials similar to those of the first light conversion material (e.g., Ce:YAG, etc.) described above with reference to Figures 3 A and 3B.
• the second light conversion material 234 may be applied onto the LED 210 using processes similar to those used to apply the first light conversion material 224 described above with reference to Figures 3 A and 3B.
• the second light conversional material 234 may be composed of different materials and/or may be applied onto the LED 210 using different techniques.
• Figure 6 is a partially schematic, top plan view of the workpiece 200 after the first and second light conversion materials 224 and 234 have been selectively applied on desired portions of the LED 210 and the second mask 230 ( Figures 5 A and 5B) has been removed.
• the LED 210 includes a plurality of uncoated or uncovered portions 240 that do not contain any light conversion materials and allow blue light to pass through.
• the LED 210 is accordingly configured to produce a desired color of light based on the arrangement of and contributions from the uncoated portions 240, the portions of first light conversion material 224, and the portions of second light conversion material 234.
• first and second light conversion materials 224 and 234 allow the LED 210 to produce any desired color of light (e.g., white light).
• any desired color of light e.g., white light.
• only two light conversion materials are described herein, in other embodiments only a single light conversion material or more than two light conversion materials may be applied onto the LED 210.
• each LED 210 on the workpiece 200 may be processed using an identical or generally identical pattern of light conversion materials.
• the pattern of light conversion material(s) on the individual LEDs 210 may vary across the workpiece 200. For example, one challenge of manufacturing microelectronic devices at the wafer level is accounting for variances in the individual microelectronic devices.
• processing variances in epitaxial growth, chemical-mechanical polishing, wet etching, and/or other operations during formation of the microelectronic devices on the same microelectronic workpiece may cause the LEDs in one region of the workpiece 200 to emit light at different wavelengths than another region.
• the emission from at least some of the LEDs may be inconsistent or off white (e.g., tinted to red, blue, and/or green).
• Embodiments of the methods described above with reference to Figures 2A-6 can address the foregoing emission variations in the LEDs across the workpiece 200 by specifically tailoring the composition of and/or arrangement of the first and second light conversion materials 224 and 234 for individual LEDs 210.
• a pattern of selectively applied light conversion materials can be used for multiple LEDs in a particular region on the workpiece 200.
• an operator may measure the emission characteristics of selected LEDs 210 on the workpiece 200 as representative for a region of individual LEDs 210.
• measured emission characteristics may be averaged, filtered, and/or otherwise manipulated to derive a value as representative for a region of the individual LEDs 210.
• workpieces to be processed may be sorted beforehand so that a first batch of workpieces having similar emission characteristics can be processed together using a first selected pattern of light conversion materials for device on the individual workpieces, a second batch of workpieces can be processed together using a second pattern of light conversion materials for devices on the individual workpieces, and so on.
• Figures 7 and 8 illustrate two additional embodiments of methods for selectively applying light conversion materials onto microelectronic workpieces as described above with respect to Figures 2A-6. In each of Figures 7 and 8, several of the features may be the same as those discussed above in connection with the workpiece 200 of Figures 2A-6. Accordingly, like reference numbers refer to like components in Figure 2A-6 and Figures 7 and 8.
• Figure 7, is a partially schematic, top plan view of a workpiece 300 having light conversion materials applied on the LED 210 in accordance with another embodiment of the technology. More specifically, the workpiece 300 differs from the workpiece 200 shown in Figures 2A-6 in that a first light conversion material 324 and a second light conversion material 334 have been selectively applied onto the LED 210 in a different pattern than the first and second light conversion materials 224 and 234 of Figure 6.
• the first light conversion material 324 includes a plurality of generally concentric circles across the LED 210. Other shapes, e.g., triangular, hexagonal, etc., are also contemplated.
• the individual circular portions of the first light conversion material 324 are separated by channels or gaps 325. A portion of these channels or gaps 325 comprise uncoated regions 340 that allow blue light from the LED 210 to pass through.
• FIG 8 is a partially schematic, top plan view of a workpiece 400 having light conversion materials applied onto the LED 210 in accordance with still another embodiment of the technology.
• the workpiece 400 differs from the workpieces 200 and 300 described above with reference to Figures 2A-7 in that a first light conversion material 424 has been applied onto the LED 210 in a plurality of individual rectilinear portions across the LED 210.
• the individual rectilinear portions of the first light conversion material 424 are separated by channels or gaps 425.
• Individual portions of a second light conversion material 434 are applied onto the LED 210 in a pattern generally corresponding to the arrangement of the rectilinear portions of the first light conversion materials 424.
• portions of the first and/or second light conversion materials can be selectively applied onto the LED 210 in other shapes (e.g., polygonal) or suitable patterns.

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• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Power Engineering (AREA)
• Led Device Packages (AREA)
• Led Devices (AREA)

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• 2010
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